Transducers are known, such as actuators and sensors that perform conversion between mechanical energy and electric energy, or speakers and microphones that perform conversion between acoustic energy and electric energy. To form highly flexible, compact, and lightweight transducers, polymer materials such as dielectric elastomers are useful. For example, an actuator can be formed with a pair of electrodes arranged on both front and back surfaces of a dielectric layer of a dielectric elastomer. A capacitance-type sensor can also be formed with electrodes with a dielectric layer interposed therebetween.
In the actuators and sensors of this type, it is desirable that the electrodes are expandable and contractible in accordance with deformation of the dielectric layer. To form flexible electrodes, conductive materials have been developed that are formed by blending conductive carbon black or metal powder in a binder such as an elastomer. For example, Patent Document 1 discloses an electrode obtained by blending particular carbon nanotubes having a three dimensional shape and carbon black in an elastomer. Patent Document 2 discloses an electrode obtained by blending carbon nanotubes in a base rubber.